Electrode for use in the contact process of making sulphuric acid



Patented Dec. 15, 1925. r

UNITED STATES PATENT OFFICE.

FRANZ VORLKNDER AND HERMANN WEBER, 0F WOLFEN, KREIS IBITTERFELD, GER- MANY, ASSIGNORS TQ AC'IIEN GESELLSCHAFT FUR- ANILIN FABRIKATION, OF

BERLIN, GERMANY.

ELECTRODE FOR USE IN THE CONTACT PROCESS OF MAKING SULPHUBIC ACID.

No Drawing.

To all whom "it may concern:

Be it known that we, (1) FRANZ Von- LiiNoEn and (2) HERMANN vvEBER, citizens of Germany, residing at (1) VVolfen, Kreis Bitterfel'd, -Germany, (2) \Volfen, Kreis Bitterfeld, Germany, have invented certain new and useful Improvements in Electrodes forUse in the Contact Process of Making Sulphuric Acid, of which the following is a specification.

This invention relates to an improvement in the contact process of making sulphuric acid and more particularly to an improvement in the method of removing arsenious compounds from the burner gases. I The burner gases, as is well known,.are purified before they are passed through the contact mass, to remove above all arsenious compounds. One method now generally used consists in passing the burner gases at a temperature below 100 C. preferably in the presence of diluted sulphuric acid, through an electric precipitator where the arsenious compounds are precipitated.

As material for the current conductors and the suspension frame for the discharge electrodes, lead was first used because of its corrosion-resisting properties. However, lead is a soft metal and for this reason it is not well suited for the particular purpose, inasmuch as it is imperative for continued successful operation of a precipitator that the inter-electrode distances be maintained in a fixed predetermined relation.

To obtain a rigid electrode system suitable for the particular purpose, it was necessary to use iron homogeneously coated with lead.

Experience has shown, however, that a strictly homogeneous coating is difficult to obtain, even with the greatest care, and has under the particular conditions of operation only a limited period of usefulness. As soon as the lead coat becomes ineffective and the iron surface is exposed to the action of diluted sulphuric acid in the presence of arsenious compounds, there is formed arsenious hydride which represents the well known contact poison.

It is the object of the present invention to provide an electrode system for the purification of burner gases, which has the necessary degree of rigidity and at the same time avoids the formation of arsine.

Application filed June 29, 1925. Serial No. 40,450.

Generally expressed, the invention comprises an electrode system in which the frame material is such that in the presence of sulphuric acid no hydrogen can be evolved.

While various materials, metals or nonmetals, may be found available, we found that copper and hard wood are particularly suitable. They are coated with lead in the usual way. 'When due to an injury or any cause whatever, a surface of the frame material is exposed, no arsine can be formed as the result thereof.

In fact, for various frame parts where no conductive coating is needed, hard wood need not even be coated with lead.

By using as frame members for electrodes and suspension frames materials according to this invention, the process of purification can be carried out with certainty of the expected results.

We claim:

1. In the art of making sulphuric acid by the contact process, an electric precipitator the electrodes of which are composed of frame elements carrying a coat of lead, the frame elements consisting of material which does not react upon sulphuric acid evolving hydrogen.

2. In the art of making sulphuric acid by the contact process,.an electric precipitator including discharge electrodes composed of frame elements carrying a coat of lead, the frame elements consisting of a material which does not react upon sulphuric acid evolving hydrogen.

3. In the art of making sulphuric acid by the contact process, an electric precipitator including discharge electrodes composed of frame elements carrying a coat of lead, the frame elements consisting of a nonmetallic material chemically inert toward sulphuric acid.

4. In the art of making sulphuric acid by the contact process, an electric precipitator including discharge electrodes composed of frame elements carrying a coat of lead, the frame elements consisting of a non-metallic material having the characteristics of hard wood.

5. In the art of making sulphuric acid by the contact process, an electric precipitator for purifying burner gases, having parts exposed to the action of the gases composed of a material which does not react upon sulphuric acid evolving hydrogen.

6. In the art of making sulphuric acid by the contact process, an electric precipi- 5 tator for purifying burner gases, having parts exposed to the action of the gases composed of a non-metallic material having the characteristics of hard wood.

7. In the art of making sulphuric acid 10 by the contact process, an electric precipitator for purifying burner gases, having parts exposed to the action of the gases composed of a material which does not react upon sulphuric acid evolving hydrogen, and provided with a coat of lead.

In testimony whereof, We afiix our signatures.

FRANZ VORLANDER. HERMANN WEBER. 

